The invention relates to fluid flow machines in general, and more particularly to improvements in machines which can be used as vacuum vane pumps or vane compressors.
A vane pump can comprise one or more stages, and each stage of a standard vane pump comprises a rotor which is secured to a motor-driven shaft and is spacedly surrounded by an eccentrically mounted housing. The peripheral surface of the rotor has one or more substantially radially extending axially parallel slots for vanes which tend to move radially outwardly and abut the internal surface of the eccentrically mounted housing when the rotor is driven. It is also known to mount the rotor and the housing in an annular wall which carries two end walls flanking the rotor and the housing. If such pump is to be used for the generation of high vacua, its parts must be machined and assembled with a high degree of accuracy. The situation is aggravated if the vacuum pump is a multistage pump. Precise axial and radial positioning of each housing and precise axial positioning of each rotor takes up much time and must be carried out by skilled persons. The procedure is repeated, with renewed losses in time, when a dismantled high vacuum vane pump is to be reassembled subsequent to inspection, repair or replacement of one or more parts.
Examples of conventional vane pumps are those disclosed in German Pat. No. 807,977 Ganster, in German Pat. No. 564,528 to Stiebling, in Swiss Pat. No. 257521 to Wuthrich and in published German patent application No. 36 03 809 of Kossek. The patent to Ganster proposes to surround the rotor with a slotted sleeve which has an internal surface engageable by the radially movable vanes of the rotor, and the diameter of such internal surface is adjustable in order to compensate for wear as a result of sliding engagement between the radially outermost portions of the vanes and the slotted sleeve. Stiebling discloses a cylindrical sleeve which surrounds and is biased against the rotor of the machine (which is used as a compressor) by a spring-biased yoke. Wuthrich discloses a vane pump wherein the rotor is surrounded by a radially movable housing; the latter has a slot for the treated fluid and its position relative to the rotor (in the radial direction of the rotor) is changed automatically as a function of changes of pressure of the conveyed fluid medium. Kossek discloses a two-stage vane pump and is concerned with automatic evacuation of condensate.